jeffrey - on behalf of all engineers on the list, let me say Welcome to
the list :-)
(I generally understood most of what you wrote - and I haven't even
googled yet )
On 1/27/10 4:14 PM, jeffrey marousek wrote:
unless the facility is using stat-mux's, 1080i is encoded at 15mbps
and 720p at 8-10mbps. those 2 numbers are rarely interfered with. the
sub-channels run at 1-3 mbps usually in an sd application.
there are exceptions to that rule. I have seen 2 1080i's muxed
together, but it looks like crap. and most vendors/integrators will be
happy to sell you stuff that operates/compresses more than that, but
they are very careful to put in the contract that the video quality
cannot be guaranteed.
but your point is also valid depending on what the mux does and what
the PSIP has told the decoder/recording device to do with all of the
null packets. some stations chose to use the null for overflow, some
do not.
and, given this is a TW system, when they flop it to QAM from
SMPTE310, what format are they putting it in at that point? 256QAM
almost perfectly fits 2 ATSC channels into one, but there are cable
companies who put 4-8 on one analog (i hate the phone calls from those
viewers). our re-trans agreements specifically address this, and say
that no further compression is to be done, but here in the middle of
nowhere, the smaller systems simply say fine, you are not going to be
on our system. (don't even get me started as to what the satellite
companies do with it)
jeff
On Wed, Jan 27, 2010 at 2:47 PM, scruffy <[email protected]
<mailto:[email protected]>> wrote:
On Jan 27, 2010, at 2:19 PM, jeffrey marousek wrote:
> I am not familiar with TW devices (other than the myriad of
complaints I have heard about their service/equipment). But, all
digital signals are not created equal. Different resolutions will
have different storage requirements. 1080i requires more than
720p. CBS and NBC are 1080i, FOX and ABC are 720p, so yes, CBS
will take more space than ABC.
theoretically, but it would also depend on how many subchannels
the station has sucking bandwidth from the main HD channel. hey,
you can never have too many weather and radar channels...
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